What’s in the Sky this December?

Article written by: Ria Mee, Education Officer

The long cold dark nights have well and truly settled in, and now that it’s December it’s officially acceptable to say the C word. Christmas, Christmas is coming! And so is Santa Claus! Decorations are going up, there’s a mad panic to buy Christmas presents and families are organising who’s having dinner and where. Ahh I love this time of year. Now, there is a silver lining, this December there are so many fascinating celestial objects that we can see in our night sky, so let’s take a look.

First things first, on 7th December there will be a New Moon. The Moon will be located on the same side of the Earth as the Sun and so not visible in the night sky. This means it’s an excellent time to go stargazing as the sky is much darker making it much easier to see fainter objects in the December night sky.

The three bright stars marking Orion’s belt and Betelgeuse and Rigel is easily visible in the sky. Credit: Stellarium/Ria Mee/Armagh Observatory and Planetarium

On that note, one of the most famous constellations visible in the December night sky is Orion the Hunter and he is a perfect starting point for introducing new stargazers to the wonders of the night sky. Orion will be rising in the sky from the east and will be visible right through until March. Probably the most recognisable feature in the constellation of Orion are the three stars marking his belt, their names are Alnitak, Alnilam and Mintaka, and they can be found in a short straight row evenly spread out in the sky. Finding the belt of Orion is the easiest way to find the constellation of Orion. His belt is what we call an asterism, which is a well-known group of stars, usually part of a much larger constellation. Two famous examples of an asterism include The Plough, found in the constellation of Ursa Major the Great Bear, which is visible all year round, and  the Summer Triangle, which on the other hand is made up of three bright stars each from three different constellations.

Marking the foot of Orion the Hunter is a blue supergiant star called Rigel, which is the brightest star in the constellation of Orion and 6th brightest star in our sky. Rigel is a relatively young star, around 8 million years old and 800 lightyears from Earth. This contrasts with the star marking Orion’s shoulder called Betelgeuse. This star is approximately 10 million years old and is essentially dying. This red giant star is 900 times the size of our sun and destined to explode as a supernova someday soon by astronomical terms, but unfortunately for us we won’t be around to witness this spectacular sight.

Now Greek mythology tells us that through Orion’s parentage, his father being Poseidon, Orion had the ability to walk on water, which is how he reached the Greek Island of Chios. After a night of heavy drinking (as many do on the Greek Islands), Orion started behaving badly and made advances towards Merope the daughter of the local King Oenopion. Furious, King Oenopion blinded Orion and banished him from the Island. Although blinded Orion managed to make his way to the Island of Lemnos, where he was helped by Hephaestus and his servant to make his way east to the Sun God Helios, who he convinced to restore his eyesight. Orion then travelled to the Island of Crete along with the huntress Artemis and her mother Leto, while in Crete he boasted that he would kill every animal in the world. This angered the Goddess of the Earth Gaia who sent down a giant scorpion to killed Orion. After Orion was killed by a sting, Artemis and Leto asked Zeus the king of the Gods to put their fellow hunter up into the skies. Zeus agreed, however he also placed up into the heavens the Scorpion that killed him forever chasing him in the sky. Rightly so if you ask me!

The Orion Nebula (Messier 42) where bright younger stars are born. Credit: NASA

Another delight found in Orion, located near his sword, is the the Orion Nebula (Messier 42), which is a complex cloud of gas. The easiest way to find the Nebula is by finding Orion’s belt and moving slightly downwards. Although visible to the naked eye, it will appear as a small fuzzy smudge, but if you have a pair of binoculars or telescope you will be able to see it in all its glory. The Orion Nebula is the closest star forming cluster to Earth, at a not so distant 1500 light-years away, and has been explored extensively by the Hubble Telescope.

The shortest day of the year will be Friday 21st December, which is also known as the winter solstice. There will only be seven hours, 49 minutes and 41 seconds of sun light here in Armagh. This is an impressive 9 hours less of sunlight compared to the longest day of the year in June. If you don’t enjoy the long dark days of going to work and coming home from work in the dark you will be glad to hear that the days do indeed start to get longer after the winter solstice.

Approaching the end of December, when we are all sick of the sight of roast dinners, we can see a very impressive asterism called the Winter Circle, sometimes known as the Winter Hexagon. It is made up of seven bright stars and is visible in the sky from December right through to March. The seven stars that make up the Winter Circle are called Rigel, Aldebaran, Capella, Procyon, Sirius, Castor and Pollux, all of which can be found in six different constellations.

Here we can see the Geminids Meteor shower radiating from the constellation of Gemini. Credit: Stellarium/Ria Mee/Armagh Observatory and Planetarium

Now who doesn’t love a good meteor shower? Well, this December is the perfect month to see meteor showers in the night sky! The Geminids Meteor Shower is visible to the naked eye, you don’t need binoculars or a telescope, all you need is good clear skies and perhaps some patience. Your best chance of seeing shooting stars is in a secluded area away from towns and cities and give your eyes at least 15 minutes to adapt to the dark. The Geminids are observable from December 13th and at the peak from 14th December, with high chances of seeing around 120 meteors per hour. The source of the meteors come from the leftover material from an asteroid called 3200 Phaethon. The name Geminids derives from the constellation of Gemini as the shower emerges from this direction in the sky.

If you happen to miss the Geminids shower don’t despair, December offers yet another meteor shower later in the month. The Ursids Meteor Shower is an annual shower running between December 17-25 and produces between 5-10 meteors per hour. It will reach its maximum rate this year on the 22nd December and will originate from the constellation of Ursa Minor. Unfortunately, this year there will be a full moon making it more difficult to see the Ursids Meteor shower, only the brightest meteors will be seen. However, if this hasn’t put you off, the best chance to see the shower is shortly after midnight. Now unlike the Geminids meteors, which is debris from an asteroid, the Ursids meteors are left over debris from Comet Tuttle, which was discovered back in 1790.

Beautiful image of the Full Moon. Credit: NASA

Now the most important question off all this December is, will we be able to see Santa Claus this Christmas Eve? Well the answer is YES! The December 24th the moon will almost be full making for nice bright skies to help you get a glimpse of the big red guy. Now we all know that Santa comes from the east so don’t forget to look this direction, if you don’t know where east is look where the Sun rises in the morning.

So that is the end of another year and another Night Sky article, I hope you have enjoyed the read and on behalf of the Armagh Observatory and Planetarium I’d like to wish you all a Merry Christmas and Happy New Year!